The silane coupling agents containing alkoxysilane groups have the functions of affording hydrophobic properties to the surface of the inorganic or organic materials and readily introducing reactive groups into these materials, and hence have been employed as a surface modifier. However, there have up to now been unknown alkoxysilane compounds which afford hydrophilic properties.
On the other hand, there has been known betaine as a compound exhibiting superior hydrophilicity. For example, it is disclosed in U.S. Pat. No. 3,671,502 that a copolymer of N-methacryloyloxyethyl-N,N-dimethyl-N-(3-sulfopropyl) ammonium betaine and 2-hydroxyethyl methacrylate exhibits higher hydrophilicity than poly (2-hydroxyethyl methacrylate) known as a hydrophilic high molecular material. However, these compounds do not contain, alkoxysilane groups and betaine groups simultaneously.
There is also described in Japanese Patent Kohyo No.61-500918 a method for introducing a phosphatidyl choline group onto the surface of a hydroxyl group-containing substance for providing a compound to improve biocompatible surface. Although the phosphatidyl choline group is capable of exhibiting superior hydrophilicity, it is inferior in resitance against hydrolysis and in long-term stability.
Among the currently employed contact lenses, there are a hard contact lens produced by polymerizing mainly a monomer such as methyl methacrylate, a semi-hard contact lens produced by polymerizing mainly a monomer such as butyl methacrylate, and a soft contact lens produced by polymerizing mainly a hydrophilic monomer such as 2-hydroxyethyl methacrylate. Of these, the hard contact lens is free of water content and hence superior in hygienic properties. However, it is insufficient in oxygen permeability required for providing satisfactory cornea metabolism to permit continuous wearing. Although the semi-hard contact lens exhibits pliability to some extent and hence is superior in wearing properties, it is poor in oxygen permeability and shape stability. On the other hand, the soft contact lens has water content therein and hence is superior to the hard or semi-hard contact lens in wearing properties. However, it is hygienically unsatisfactory and presents maintenance problems, such as necessity of daily boiling for sterilization.
For eliminating the above-described inconvenience of the prior art contact lenses, high oxygen permeable hard contact lens is recently becoming more popular in the contact lens market. This type of contact lens is mainly formed of silicone-based polymers, such as polysiloxane or silicon-containing methacrylate polymer, and is relatively satisfactory in safety to living bodies. However, the silicone-based polymer by itself is low in strength and has a problem in workability, so that it becomes necessary to increase the lens thickness or to employ reinforcing materials.
Various proposals have been made for improving strength of the silicone-based polymer. For example, in Japanese Patent Publications Nos.62-8762 and 63-36646 a copolymer mainly containing silicon-containing methacrylate and fluorine-containing methacrylate is proposed. On the other hand, in U.S. Pat. Nos. 3,419,634 and 3,419,635 a silicone-polycarbonate copolymer is proposed. However, the copolymers having high oxygen permeability are inferior in wearing properties and wearing agreeability, although the copolymers exhibit acceptable high strength.
It is an object of the present invention to provide a novel alkoxysilane compound which contains both the alkoxysilane group and the betaine group, which is capable of affording hydrophilicity to various materials and which gives superior resistance against hydrolysis after affording hydrophilicity.
It is another object of the present invention to provide a surface processing solution which is capable of improving hydrophilicity of the surfaces of various materials and particularly the wearing properties and wearing agreeability of the contact lens and which is capable of affording contamination proofness and detachment preventative properties of the contact lens.
It is a further object of the present invention to provide a surface processing solution capable of affording a surface processed layer superior in anti-hydrolytic properties.
It is yet another object of the present invention to provide a contact lens which is superior in wearing properties and wearing agreeability and exhibits contamination proofness and detachment preventative properties.